Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())

mp = ['#'*(W+1)]
memo = [[-1]*(W+1) for _ in range(H+1)]

cnt = 0
for _ in range(H):
  s = '#'+input()
  cnt += s.count('.')
  mp.append(s)
  
ds = [[1,0], [-1,0], [0,1], [0,-1]]
h = deque([[1,1,1]])
while h:
  l = h.popleft()
  for d in ds:
    if l[0]+d[0] <= W and l[1]+d[1] <= H:
      if mp[l[1]+d[1]][l[0]+d[0]] == '.' and memo[l[1]+d[1]][l[0]+d[0]] == -1:
        memo[l[1]+d[1]][l[0]+d[0]] = l[2] + 1
        h.append([l[0]+d[0], l[1]+d[1], l[2] + 1])
  if memo[H][W] > -1:
    print(cnt-memo[H][W])
    exit()
    
print(memo[H][W])